WASHINGTON (AP) — A rare full appeals court Monday wrestled with whether it should overturn the conviction of an alleged al-Qaida propagandist, who argues the acts he was convicted for were not considered crimes at the time he committed them.

Ali Hamza al-Bahlul was convicted for providing material support for terrorism, conspiracy and solicitation to commit war crimes for making propaganda videos for al-Qaida. A three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit threw out the convictions in January. The full court vacated that ruling in April and said it would take another look at the case.

A Justice Department lawyer, Ian Gershengorn, told the judges at Monday’s hearing that the initial ruling has led to uncertainty in other Guantanamo cases. He said that 9/11 defendants have filed motions seeking to get their convictions dismissed as a result of the ruling.

But Chief Judge Merrick B. Garland questioned whether that was because of the court’s ruling, or because of the charges that the government brought, adding that prosecutors could have charged the men with other offenses. He said that the uncertainty wasn’t the court’s fault.

And Judge Brett M. Kavanaugh said that the earlier ruling, while significant, was “not a release order.”

“We agree, it’s not a release order,” Gershengorn replied.

January’s ruling resulted from a previous appeals court panel’s decision last October overturning the conviction of Osama bin Laden’s former driver. The driver, Salim Ahmed Hamdan, served a prison term for material support for terrorism, but the appeals court ruled that before enactment of the Military Commissions Act of 2006, only violations of the international law of war and pre-existing federal offenses were subject to trial by military commission. Hamdan’s alleged material support for terrorism pre-dated the 2006 law and was not a war crime under international law at the time he engaged in the activity for which he was convicted, the court concluded.

Al-Bahlul and Hamdan were the only prisoners convicted in a trial by the tribunals known as a military commission. The five other convictions of Guantanamo prisoners came through plea bargains.

In taking up the case of al-Bahlul, the full court asked the two sides to address whether the Constitution’s bar against ex post facto convictions for violating laws that were not in place when an alleged crime occurred applies to detainees at Guantanamo; and whether conspiracy was a violation of the international law of war at the time of al-Bahlul’s offense.

Al-Bahlul’s lawyer, Michel Paradis, said his client can’t be tried for crimes “that did not exist when is alleged to have committed them.” There is no law, he added, that al-Bahlul could have looked to know that the acts he committed were crimes.

In court papers, Paradis acknowledged that his client has admitted he’s a member of al-Qaida, but that he didn’t have foreknowledge and didn’t participate in any terrorist attack. Paradis wrote that the military commission trial was about al-Bahlul’s film, known by various titles, including “The Destruction of the American Destroyer the U.S.S. Cole.”

“The prohibition against ex post facto laws is among the most fundamental protections contained in the Constitution,” Paradis wrote.

Gershengorn, the Justice Department lawyer, told the court that in passing the Military Commissions Act of 2006, it was clear Congress intended to cover the activities of Guantanamo detainees committed before passage of the law. He said that there’s a long history of trying defendants for conspiracy in military commissions, including the trial of the men involved in the assassination of President Abraham Lincoln.

The decision by the full appeals court to rehear the al-Bahlul case, known as an “en banc,” is unusual. According to the D.C. Circuit rules, an en banc rehearing ordinarily will not be ordered unless it is necessary to secure or maintain uniformity of the court’s decisions, or the proceeding involves a “question of exceptional importance.”

Seven of the eight active members of the court participated Monday; the eighth, Sri Srinivasan, joined the court after it had decided to take up the case and did not participate.